Seasonal Migrational Behaviour in Irish Giant Deer Megaloceros giganteus (Blumenbach, 1799); An investigation of intra-tooth multi-isotope analysis application in palaeontological migration studies

Abstract

The giant deer Megaloceros giganteus (Blumenbach, 1799) is an icon of the Ice Age due to their famous antlers, and is commonly found in Pleistocene marl deposits throughout Ireland. While the topic of their migrational behaviour has been suggested, mainly due to this behaviour being common in deer species today, it has never been researched. Similarly little research on the isotopic composition of giant deer has been conducted. Therefore, migrational behaviour and seasonal movement are suggested to be analysed in three giant deer from Ireland dating back to the Pleistocene Late Glacial through isotopic analysis. Analysis through sequential intra-tooth sampling for 87Sr/86Sr ratios is suggested and should be acquired from TIMS and MC-ICPMS on the giant deer’s tooth enamel. Although issues are suggested for 87Sr/86Sr isotope research due to factors such as reservoir times of strontium in the body, studies on modern caribou suggest the validity of such analysis for the brachydont molars of cervids. Possible reasons for migrational behaviour are explored. As a deer species, giant deer required a high nutrient uptake for antler growth and were not as well adapted for the cold-dry steppe environments of the Pleistocene glacials. These stresses would have made migrational behaviour beneficial for maximising nutrient uptake during the warmer months, and for avoiding the harshest winter conditions of the glacials by moving to sheltered, low lying areas. Giant deer from interglacials of the Pleistocene would have not been under the same stresses, as the closed environments of that period allowed for the mix-feeding strategies they likely employed. Irish giant deer may have been pushed to migrational behaviour especially by the onset of the Younger Dryas cold stage as the preferred lime-rich grasses and forbs they depended on disappeared from the island. Therefore, migrational behaviour and seasonal mobility strategies may have been paramount for giant deer during cold periods of the Pleistocene and should therefore be analysed through sequential sampling of enamel for 87Sr/86Sr ratios.